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Biomedical subjects

D Chu

Publications and source records attributed to D Chu.

At least 55 records · Page 3Linked to original sources
PubMed1991

Single photon emission computed tomography using 99mTc-HM-PAO in the routine evaluation of Alzheimer's disease.

Regional cerebral blood flow was studied in 7 patients with clinically suspected Alzheimer's disease and 10 normal controls by single photon computed emission tomography (SPECT) using HM-PAO. All patients with Alzheimer's disease and no controls had parietal lobe hypoperfusion which was usually bilateral. In patients with more severe dementia hypoperfusion extended into the frontal lobes. Parietal lobe hypoperfusion corresponds to parietal lobe degeneration which is the one of the first neocortical regions to show the typical degenerative changes of Alzheimer's disease. SPECT with HM-PAO is a non-invasive investigation available in most nuclear medicine departments and complements existing tests in the routine evaluation of patients presenting with dementia.

Aged↗
PubMed1990

Translocation (X;12)(q27;q14) in a lipoma.

Cytogenetic analysis by short-term culture of a lipoma from the posterior neck region of a 63-year-old man showed a t(X;12)(q27;q14) as the sole chromosomal abnormality. Rearrangement of band 12q14 is nonrandom in lipomas, although its involvement with a sex chromosome has not been reported earlier.

Cells, Cultured↗
PubMed1990

[F3, a fractionated extract of Astragalus membranaceus, potentiates lymphokine-activated killer cell cytotoxicity generated by low-dose recombinant interleukin-2].

Success with rIL-2 immunotherapy of human cancer appears to depend on the administration of high doses which are frequently associated with excessive toxicity. Future use of rIL-2 will require certain modifications based on the use of lower doses of rIL-2 without significant loss of antitumor efficacy. The authors tested in vitro the possibility of potentiating the activity of rIL-2 in terms of LAK cell generation. The authors hypothesized that co-incubation of LAK cell precursors with a Chinese herbal extract (F3) of Astragalus membranaceus (an immune modulator currently under study in the authors' laboratory), along with a low concentration of rIL-2 would generate levels of LAK cell activity equivalent to those generated by high concentrations of rIL-2 alone. The authors found: (1) a 10-fold potentiation of rIL-2 activity manifested by tumor cell killing activity of 80% resulting from LAK cell generation with F3 plus 100 u/ml of rIL-2 versus 76% generated by 1000 u/ml of rIL-2 alone; (2) a significant reduction in the number of effector LAK cells required for equicytotoxic reaction following LAK cell generation with F3 plus rIL-2 compared to rIL-2 alone. The authors conclude that potentiation of antitumor activity mediated by rIL-2 in low concentrations is possible by the concomitant use of another immune modulator such as Astragalus membranaceus.

Astragalus propinquus↗
PubMed1989

Plasma concentration of atrial natriuretic peptide in different phases of Korean hemorrhagic fever.

Korean hemorrhagic fever (KHF) is an epidemic viral disease characterized by high fever, hemorrhagic tendency and renal failure, and by hemorrhages of right atrium and renal medulla as well as necrosis of anterior hypophysis. Plasma immunoreactive atrial natriuretic peptide (irANP) levels of 15 patients in the oliguric phase was 94.8 +/- 8.4 pg/ml (mean +/- SEM), 80% higher than of the normal control group (53.0 +/- 4.7 pg/ml; n = 28). In the diuretic phase it declined to 63.7 +/- 5.3 pg/ml (n = 26). Plasma renin activity (PRA) in the oliguric phase was 19.0 +/- 1.3 ng AI/ml/h, and in the diuretic phase 5.3 +/- 0.9 ng AI/ml/h, significantly higher than the control value (2.5 +/- 0.1 ng AI/ml/h). Elevations of irANP and PRA were not correlated in each group. Also systemic blood pressure as well as heart beats were significantly increased in the oliguric phase. These findings suggest that the increased irANP may have resulted from increased circulatory volume and that the ANP secretory process may not be affected by the disease.

Acute Kidney Injury↗
PubMed1988

Management of airway problems in lung cancer patients using the neodymium-yttrium-aluminum-garnet (Nd-YAG) laser and endobronchial radiotherapy.

This study summarizes our experience in the evolution of a management technique for unresectable or recurrent lung cancer using the neodymium-yttrium-aluminum-garnet (Nd-YAG) laser with high-dose endobronchial brachytherapy. The laser gave good palliation for hemoptysis and obstruction with a low complication rate, and the addition of endobronchial radiotherapy was a useful adjunct for maintaining airway patency. High-dose brachytherapy delivered by the Gammamed IIi remote afterloader proved to be the best method of delivering this treatment.

Adult↗
PubMed1985

Tension and compression in the cytoskeleton of PC 12 neurites.

We report in this article that the retraction of PC 12 neurites, unlike that of other cultured neurons, is due to tension within the neurite. Retraction is rapid and independent of metabolic energy. Transection of one arm of a branched neurite immediately causes the remaining arm to take up a new equilibrium position between attachment points. Similarly, detachment of one growth cone of a cell causes the cell body to move to a new equilibrium position between the remaining neurites. These observations provide direct evidence for the suspension of the cell soma among a network of tensioned neurites. We used retraction as an assay for neurite tension to examine the role of actin filaments and microtubules in neurite support and elongation. Our data suggest that microtubules (MTs) within PC 12 neurites are under compression, supporting tension within the actin network. Treatment of cells with drugs that disrupt actin networks, cytochalasin D or erythro-9-[3-(2-hydroxynonyl)]adenosine eliminates retraction regardless of the absence of MTs, lack of adhesion to the substratum, or integrity of the neurite. Conversely, stimulation of actin polymerization by injection of phalloidin causes retraction of neurites. Treatments that depolymerize MTs, nocodazole or cold, cause retraction of neurites, which suggests that microtubules support this tension, i.e., are under compression. Stabilization of MTs with taxol stabilizes neurites to retraction and under appropriate circumstances can drive neurite extension. Taxol-stimulated neurite extension is augmented by combined treatment with anti-actin drugs. This is consistent with the actin network's normally exerting a force opposite that of MT assembly. Cytochalasin and erythro-9-[3-(2-hydroxynonyl)] adenosine were found to increase slightly the dose of nocodazole required for MT depolymerization. This is consistent with the postulated balance of forces and also suggests that alteration of the compression borne by the microtubules could serve as a local regulator for MT polymerization during neurite outgrowth.

Actins↗
PubMed1984

Spatial organization of axonal microtubules.

Several workers have found that axonal microtubules have a uniform polarity orientation. It is the "+" end of the polymer that is distal to the cell body. The experiments reported here investigate whether this high degree of organization can be accounted for on the basis of structures or mechanisms within the axon. Substantial depolymerization of axonal microtubules was observed in isolated, postganglionic sympathetic nerve fibers of the cat subjected to cold treatment; generally less than 10% of the original number of microtubules/micron 2 remained in cross section. The number of cold stable MTs that remained was not correlated with axonal area and they were also found within Schwann cells. Microtubules were allowed to repolymerize and the polarity orientation of the reassembled microtubules was determined. In fibers from four cats, a majority of reassembled microtubules returned with the original polarity orientation. However, in no case was the polarity orientation as uniform as the original organization. The degree to which the original orientation returned in a fiber was correlated with the number of cold-stable microtubules in the fiber. We suggest that stable microtubule fragments serve as nucleating elements for microtubule assembly and play a role in the spatial organization of neuronal microtubules. The extremely rapid reassembly of microtubules that we observed, returning to near control levels within the first 5 min, supports microtubule elongation from a nucleus. However, in three of four fibers examined this initial assembly was followed by an equally rapid, but transient decline in microtubule number to a value that was significantly different than the initial peak. This observation is difficult to interpret; however, a similar transient peak has been reported upon repolymerization of spindle microtubules after pressure induced depolymerization.

Animals↗
PubMed1982

Antihypertensive effect of tiapamil, a calcium antagonist. Double-blind placebo crossover study.

The antihypertensive effects of intravenously and orally administered tiapamil and placebo were compared in 6 male patients (60 +/- 5 years: mean +/- SD) with mild essential hypertension (WHO classification Stage I) in a randomized double-blind crossover procedure. In the intravenous study, 1 mg/kg loading dose of tiapamil (or placebo) was followed by 50 micrograms/kg/min tiapamil or placebo over 2 h. In the oral study, the patients received placebo or approximately 6 mg/kg tiapamil. Blood pressure (BP) was determined by the Hawksley Random Zero Sphygmomanometer. Heart rate (HR) and P-R interval were derived from ECGs. Statistical significance was assessed by the paired Student's test. While intravenously administered placebo transiently increased both BP and HR, intravenous tiapamil significantly (p less than or equal to 0.05) lowered both variables. The P-R interval was also transiently but significantly (p less than or equal to 0.05) increased by intravenous tiapamil. Similarly, orally administered tiapamil showed an antihypertensive effect which was not observed with placebo. Neither HR nor P-R interval was influenced by oral tiapamil. The results suggest that tiapamil is an effective but short-acting antihypertensive agent.

Administration, Oral↗
PubMed1982

Antagonism of aldosterone in normal subjects by Ro 12-2503 and spironolactone.

The potency and efficacy of a single dose of a new aldosterone antagonist, potassium 17 a-hydroxy-6 beta, 7 beta-methylene-3-oxo-D-homo-17a alpha-pregna-4,16-diene-21-carboxylate (Ro 12-2503), in reversing the renal effects of exogenous aldosterone were compared to those of spironolactone, and placebo. The study was performed according to double-blind and crossover procedure in six healthy male subjects. Both drugs, spironolactone and Ro 12-2503, did not completely antagonize the effects of aldosterone. The efficacy of Ro 12-2503 in terms of the urinary Na+/K+ ratio and the urinary Na+ concentration was less than that of spironolactone. Spironolactone produced a slightly greater natriuresis, but the difference was not significant. The method described, based on standard bioassay techniques permits a comparison of the two drugs, and may prove useful in the screening and evaluation of aldosterone antagonists.

Adult↗
PubMed1981

Antihypertensive effects of a novel peripheral vasodilator, Ro 12-4713.

The effects of Ro 12-4713, a vasodilator, on blood pressure and heart rate, were tested in 13 ambulant patients with mild to severe hypertension. The patients received Ro 12-4713 in total oral doses ranging from 1.5 to 4 mg/kg over a 3-5 day period. Standard laboratory tests were done 24 h before and after the study. Standing and supine blood pressure and heart rate were determined before, and every hour for 6-8 h after drug administration. ECGs were recorded before, during and at the end of each study day. Ro 12-4713 reduced the pretreatment standing and supine-blood pressure from 213 +/- 34/126 +/- 21 mmHg and 218 +/- 31/130 +/- 20 mmHg to 156 +/- 33/85 +/- 9 mmHg and 158 +/- 25/88 +/- 11 mmHg at the end of Day 5. Heart rate was only transiently increased in patients with pretreatment values of less than 90 beats/min. Although abnormal ECGs tended towards normalization, there were 2 cases of T-wave inversion (the patients remained asymptomatic). Raised BUN levels tended to decrease towards normal. Side effects reported spontaneously by patients (headaches, palpitations, dizziness, nausea and one case of water retention) appeared to be transient in nature. Ro 12-4713 appeared to be a very potent and long lasting antihypertensive agent, whose inherent side effects were only transient in nature.

Aged↗
PubMed1981

Serial M-mode echocardiography in evaluation of the cardiovascular effects of tiapamil and their relationship to plasma levels in patients with coronary heart disease.

Tiapamil (Ro 11-1781) is a new calcium antagonist. Several investigators have reported about its efficacy against cardiac arrhythmias and angina pectoris. However, there was no study that assessed a possible relationship between hemodynamic effects and plasma concentration. Our study was aimed to investigate any possible relationship between cardiovascular effects of tiapamil and its plasma concentration. We selected 8 coronary; patients (6 males and 2 females) with a mean age of 61.9 yr and a mean weight of 70.9 kg. Tiapamil was administered per os at the dose of 250 mg t.i.d. for 4 consecutive days. Hemodynamic data were obtained by means of echocardiography, ECG and sphygmomanometry. Plasma concentrations of Ro 11-1781 and its major metabolites were measured by means of high pressure liquid chromatography. With tiapamil, the morning systolic BP fell from 130.6 +/- 19.5 (mean +/- SD, pretreatment) to 114.4 +/- 18.2 mm Hg on day 4, the change being clinically and statistically significant (P less than 0.02 by paired t-tests). Diastolic BP and HR remained unchanged. LVEDD and LVESD were not affected to any relevant extent, but VCF was significantly (P less than 0.05) and persistently increased. Tiapamil was well absorbed, but large interindividual variations were observed. As a general rule, no direct relationship between plasma concentrations and hemodynamic effects could be demonstrated. However, the number of patients is too small to allow general conclusions. At the above dose, tiapamil did not elicit any clinically detectable negative inotropic or negative chronotropic effect, probably because of its lowering effect on systolic BP.

Aged↗
PubMed1980

Antiarrhythmic effect of the calcium antagonist tiapamil (Ro 11-1781) by intravenous administration in patients with coronary heart disease.

Twenty coronary patients with a median age of 76 years were treated in the coronary care unit with tiapamil, a new Ca2+ antagonist, by intravenous infusion (until December, 1979, the generic name was dimeditiapramine). The following arrhythmias were identified: atrial fibrillation with ventricular rate greater than 95 beats/min (5 patients); supraventricular premature complexes (SVPC) (4 patients); and ventricular premature complexes (VPC), Lown grades 2-4 (15 patients). Electrocardiograms and hemodynamic parameters were continuously monitored prior to, during, and after the therapy. In patients with atrial fibrillation, sinus rhythm was not restored, but tiapamil decreased the ventricular rate by 54%. In patients with VPC, the median frequency of VPC decreased from 310.5 before tiapamil to 32.5 beats/h at the fourth hour of therapy (p less than 0.01). The median ectopic/sinus beat ratio decreased from 0.083 (pretreatment) to 0.008 at the fourth hour of infusion (p less than 0.10). In one of the patient with an insufficient decrease in the number of VPC, the VPOC changed from class 4a (pretreatment) to class 2 (during the therapy), returning to class 4a after the infusion was stopped. Tiapamil reduced the median systolic and diastolic blood pressures by 8.3 and 7.1%, respectively (p less than 0.05), the third hour. Hypotension and bradycardia were observed in 5/20 patients. The results show that tiapamil is effective against both supraventricular and ventricular arrhythmias, and thus its spectrum of action differs from that of other calcium antagonists.

Adult↗
PubMed1980

Influence of propranolol and pindolol on the haemodynamic effects of papaverine, isoprenaline and noradrenaline in hypertensive patients.

The influence of two beta-adrenoceptor antagonists, propranolol and pindolol, on the haemodynamic effects of papaverine, isoprenaline and noradrenaline was investigated in 9 male patients with first degree essential hypertension. Propranolol and pindolol were given according to a doubleblind, crossover scheme. Heart rate and blood pressure were measured before and after each treatment. Propranolol 670 microgram/kg i.v. reduced the supine and standing systolic blood pressures by 2.3% and 1.6%, respectively. Similarly, the intravenous administration of pindolol 35 microgram/kg reduced supine and standing systolic blood pressure by 5.5% and 8.3% respectively (clinically insignificant). Neither drug affected diastolic blood pressure. Following propranolol, there were moderate reduction in supine and standing heart rates, respectively by 24% and 20% (p < 0.001). Similarly, but to a lesser extent, pindolol reduced supine and standing heart rate by 12% and 17% (p < 0.001). The effects of papaverine, which, at 1.5 mg/kg i.v. reduced systolic blood pressure by 5-10% and increased heart rate by 8-15%, were not significantly influenced by the beta-blockers. The blood pressure and heart rate responses to isoprenaline, on the other hand, were attenuated or inhibited by both beta-blockers. While the beta-blockers inhibited the beta-adrenoceptor component of noradrenaline, the pressor component of noradrenaline, which is mediated through the alpha-adrenoceptors, was not influenced by propranolol, but was inhibited after pindolol. It is concluded that pindolol differs qualitatively from propranolol in that it inhibited both the alpha and beta-adrenoceptor effects of noradrenaline.

Adult↗
PubMed1980

Torsades de pointes as a manifestation of mexiletine toxicity.

An episode of torsades de pointes, an unusual ventricular tachyarrhythmia, developed in a 59-year-old coronary patient who was treated with 100 mg. four times a day mexiletine orally. The PR, QRS, and QT intervals were normal. The ventricular arrhythmias resembled in part, the patient's previous ventricular premature complexes, but there were some relevant morphological differences. The plasma electrolytes were within normal limits. Mexiletine, which is chemically and electrophysiologically similar to lidocaine, probably caused this arrhythmia. Although mexiletine is a useful antiarrhythmic drug, it should be added to the list of drugs associated with atypical ventricular tachycardia.

Blood Pressure↗